1. Field of the Invention
The present invention relates to an image processing device and an image processing method, and more particularly to an image processing device and an image processing method capable of realizing a lower delay decoding process.
2. Description of the Related Art
As representative image compression methods in the related art, there are JPEG (Joint Photographic Experts Group) and JPEG2000 which are standardized by the ISO (International Standards Organization).
Recently, there have been wide studies on methods where images are divided into a plurality of bands using a filter called a filter bank constituted by a high pass filter and a low pass filter, and encoding is performed for each band. Among them, wavelet transform encoding has attracted attention as a new technique replacing a DCT (Discrete Cosine Transform) since there is no block distortion in high compression which is problematic in the DCT.
JPEG2000, which was standardized internationally in January 2001, employs a scheme where entropy encoding (bit modeling with bit plane units and arithmetic coding) with high efficiency is combined into the wavelet transform, and considerably improves encoding efficiency as compared with JPEG.
JPEG2000 has been selected as a standard codec for a digital cinema specification (DCI (digital cinema initiative) specification) and has begun to be used for compression of moving images such as movies. Also, each manufacturer has begun to manufacture products where JPEG2000 is applied to monitoring cameras, interview cameras for broadcasting stations, security recorders or the like.
De facto codecs using the wavelet transform in addition to JPEG2000 have been developed and released from each facility.
The use of these codecs in instant (real-time) data transmission is being taken into consideration. Encoding of image data, data transmission of the encoded data, and decoding of the transmitted encoded data are performed together, and thus low delay data transmission such as, for example, so-called live broadcasting is realized.
However, since JPEG2000 fundamentally performs encoding and decoding with picture units, if low delay is intended to be realized so as to be used for real-time transmission and reception, at least an amount of one picture is delayed in the encoding, and at least an amount of one picture is also delayed in the decoding.
This is true of not only JPEG2000, but also any codec such as an AVC (Advanced Video Coding) intra, JPEG, or the like. However, recently, a means has been proposed which divides an image plane into several rectangular slices or tiles, and performs encoding and decoding for each of them independently, thereby reducing delay time (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-311327).
When the above-described low delay data transmission is realized using such a codec, it is necessary for a decoder to output a predetermined amount of decoded video signals, for example, within an H blank (horizontal blank) or a V blank (vertical blank), which is one of the characteristics of the video signal.